The present invention relates generally to apparatus and methods for handling semiconductor wafers or similar articles. More particularly, the present invention relates to a robotic end effector for handling semiconductor wafers using edge-gripping techniques.
Semiconductor manufacturing requires an ultra-clean environment for the silicon wafers during the manufacturing process; therefore it is highly desirable to have few moving parts in the wafer processing environment due to the risk of wear particles and the like migrating to the wafer surface, thereby contaminating the wafer and resulting in reduced production yields. Currently, the handling of semiconductor wafers and similar articles is accomplished using complex mechanical systems that require many moving parts.
Various examples of devices for handling wafers can be found in U.S. Pat. Nos. 4,449,885, 4,553,069, 4,681,213, 4,752,180, 4,773,687, 5,011,594, 5,046,909, 5,054,834, 5,547,515, 5,555,634, 5,692,873, 5,647,626, 5,765,890, 6,077,026, 6,086,976, 6,112,735, 6,116,848, 6,120,360, and 6,283,701, the disclosures of which are hereby incorporated herein by reference in their entirety. These devices hold wafers by various methods including mechanical clamping, vacuum pressure, electrostatic attraction, adhesives, chucks, and carrying trays.
Several drawbacks with current wafer holding techniques exist. For example, multiple moving parts have inherent reliability problems and are prone to failure. Additionally, vacuum pressure, clamping, and electrostatic devices typically require complex operating systems. Also, vacuum pressure, clamping and adhesives can damage wafer surfaces.
Certain devices exist for flexibly gripping items of various shapes; however, most are not suitable for handling semiconductor wafers. Examples of such devices can be found in U.S. Pat. Nos. 4,540,034, 4,839,947, and 5,121,908, the disclosures of which are hereby incorporated herein by reference in their entirety.
The invention relates to an apparatus for handling semiconductor wafers wherein the apparatus has a minimal number of moving parts. The invention is particularly useful in the handling of semiconductor wafers of varying diameters. Further, the apparatus handles wafers in a manner that substantially reduces or eliminates the likelihood of wafer damage. In addition, the apparatus can handle wafers by gripping the edges of the wafers, thereby eliminating the need for a carrier.
In one aspect, the invention includes a robotic end effector that includes at least one arm, a flexure joint, and a force element. In various embodiments, the force element can be an electric solenoid device, a pneumatic actuator, a piezoelectric actuator, or similar devices as known to those skilled in the art. In other embodiments, the end effector includes a second arm. One or both arms can be arcuate. The arms can be approximately the same length and the arms can include fingers for contacting the edges of a wafer. Furthermore, the apparatus need not be mounted on a robotic arm.
In another aspect, the invention relates to methods of handling wafers. One method includes the steps of moving an end effector into contact with a wafer, applying a force to the end effector, and removing the force on the end effector. Applying a force to the end effector causes at least one arm of the end effector to open by rotating away from the wafer. Once the end effector has fully grasped the wafer, the opening force is effectively removed. In one embodiment, the method includes the step of actuating a force element to open the flexure joint and release the wafer.
These and other objects, along with advantages and features of the present invention herein disclosed, will become apparent through reference to the following description, the accompanying drawings, and the claims. For example, the invention is scaleable and practical for use in handling materials other than semiconductor wafers. Furthermore, it is to be understood that the features of the various embodiments described herein are not mutually exclusive and can exist in various combinations and permutations.